<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Page Title</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="screen" href="main.css" />
    <script src="main.js"></script>
    <style>
        /* .box{
            display: flex;
            width:980px;
            height:30rem;
            align-items:center;
            background:#0099cc;
        }
        h1{
            font-size:1rem;
            padding:1rem;
            border:1px dashed#FFF;
            color:#FFF
        } */
        .box{
            display: flex;
            width: 980px;
            height: 30rem;
            align-items: center;
            background: #0099cc;
        }
        h1{
            font-size: 1rem;
            padding: 1rem;
            border: 1px solid #fff;
            color: #fff;
            flex: 1;
        }
    </style>
</head>
<body>
    <div class="box">
        <h1>flex弹性布局</h1>
        <h1>flex弹性布局</h1>
        <h1>flex弹性布局</h1>
    </div>
</body>
</html>